Method and composition for lubricating under wet conditions



United States PatentO 3,001,940 METHOD AND COMPOSITION FOR LUBRICATINGUNDER WET CONDITIONS Harold J. Watson, Danville, Va., and Raymond B.Tierney, Wappingers Falls, N.Y., assignors to Texacolnc, a corporationof Delaware No Drawing.' Filed Jan. 21, 1958, Ser. No. 710,171

a 6 Claims. (Cl. 25232.7)

This invention relates to a method and composition for lubricatingmodern machinery under wet conditions and particularly to a paper makingmachine employing a lubricating oil circulating system.

This is a continuation-in-part of application Serial No. 658,021, filedMay 9, 1957, now abandoned.

The dryer section of a modern Fourdrinier paper making machine consistsof as many as one hundred steam heated dryer. rolls weighing many tonsand employing heavy journal and double roller self-aligning bearingswhich carry the dryer rolls at speeds as high as 150 rpm. The rolls aregeared together at their journals in order to synchronize their running.In addition to the paper dryers in the dryer section there are similarrolls for drying the felt used in the drying process and a greaternumber of small idler rolls over which the felt is threaded in thedrying operation. These smaller rolls also employ roller bearings andsynchronizing gears necessary for their proper operation. 7

In order to provide proper and adequate lubrication for the bearings andgears in this high speed, high pressure machinery, lubricating oilcirculating systems were found to be necessary. Where so many costlybearings and gears are involved, the circulating oil system providesadequate lubrication and also removes considerable heat, which is verydesirable.

The possibility of oil contamination by water in the circulating systemon a dryer section is always present. The water enters the oil either bycondensation of the steam in the cooler parts of the circulatingsystemor by leaks which frequently develop in the steam joints. Watercontamination is a considerably more serious problem in these modernhigh speed machines since they are lubricated with relativelywater-sensitive detergent type oils in comparison to the straightmineral oils previously used and from which the water readily separated.It has been necessary in order to ensure relatively trouble-freeoperation to exercise every precaution to keep water out of thecirculating oil system. However, despite such precautions, oilcontamination with water is prevalent in paper machine operation.

The metal sulfonates which were used to obtain the detergency desirablein prior paper machine lubricants also increased the emulsificationtendency of the mineral oil. When the water-oil emulsion was formedduring the circulation of the oil composition, the lubricating functionof the mineral oil was seriously curtailed. The oil, with theemulsifying agency of the detergent sulfonates, did not separate fromthe water sufliciently before it was recirculated, thus greatly reducingits effectiveness. Furthermore, prior to the present invention, waterwhich entered the lubricating oil composition soon leached additivesplaced in the oil for detergency, additional oxidation and corrosionprotection, and improvement ofthe extreme pressure property of the oil.

Another lubricating problem occurring in paper mawater is desirable.

chine operation is oil oxidation. Bearings and gears are temperaturesare estimated to be frequently over 275 F. 7

3,001,940 Patented Sept. 26, 1961 ice The effect of increased steampressures on lubrication has been to require a more oxidation-resistantoil. and one with suflicient load-carrying capacity at the highertemperatures to protect the bearings from failure. The comparativelyhigh contact pressures which must be maintained between the surfaces ofthe couch rolls and the calender rolls of the paper machine in order todevelop the necessary squeezing are of necessity imparted to thebearings which carry these rolls. This fact necessitates furtherconsideration of the load-carrying ability of the oil. Thus the base oilshould be fortified with an antioxidant and extreme pressure additive toobtain proper lubrication of the paper machine.

Corrosion protection of the metal partsof the machinery to be lubricatedis also a necessity because of the water present in the system.Additives functioning as corrosion inhibitors are generally incorporatedin circulating lubricants exposed to excessively moist conditions, forprotection in this respect.

The problem, therefore, which is solved by the present invention, is theadequate lubrication of a paper machine wherein the lubricantcomposition is exposed to water contamination. Thus in accordance withthis invention, the method of lubricating a paper machine comprisescirculating an oil composition through the bearings and gears of said.machine consisting essentially of a mineral lubricating base oil havingan SUS viscosity at F. of from 50 to 2500, and containing 'a detergentselected from the group consisting of alkaline earth metal, magnesium,zinc, and amine salts of .dinonylnaphthalene sulfonic acid wherein thenonyl groups are highly branched, periodically removing that portion ofwater from the system which separates from the oil composition and thenrecirculating said composition through the bearings and gears of saidmachine.

The method of the invention also includes utilizing a circulatinglubricant composition having an antioxidant additive in combination withthe dinonylnaphth-alene sulfonic acid salt incorporated therein toimprove the performance of the composition in use; The preferredadditional additive or additive combination is one which functions as anoxidation and corrosion inhibitor to prevent deterioration of themineral oil composition in service while protecting metal parts fromcorrosion. Other useful additives include extreme pressure additives,pour point depressants, etc.

The invention also includes a novel circulating oil composition forlubricating the dryer sections of paper machinery and other machineryrequiring lubrication under similar conditions in which fast separationfrom The novel composition comprises a mineral lubricating base oilhaving an SUS viscosity at 100 F. of from 50 to 2500, a compoundselected from the group consisting of alkaline earth metal, magnesium,zinc, and amine salts of dinonylnaphthalene sulfonic acid, wherein thenonyl groups are highly branched, in an amount ranging from 0.1 to 4percent by weight of the composition; and a metal dialkyldithiophosphate in an amount ranging from 0.1 to 3.0 percent by weightbased on the composition. Very advantageously, the dinonylnaphthalenesulfonic acid salt is present in the composition in'an amount from about0.5 to 2 percent by weight, and the metal dialkyl dithiophosphate ispresent in an amount from about 0.1 to 2 percent, preferably from about0.5 to 1 percent by weight of the composition. The compositionpreferably also includes from about 0.05 to 1.0 percent of a chlorinatedparaflin wax-naphthalene condensation product to reduce pour point, anda foam inhibitor, such as a 10 percent solution of dimethyl siliconepolymer in kerosene in the amount of about 100 to 300 ppm.

The salts of 'dinonylnaphthalene sulfonic acid applicable to the presentinvention and the method of their preparation are set forth in US.2,764,548 to King et al., issued September 25, 1956. Briefly, thesecompounds are prepared by dissolving dinonylnaphthalene in an organicsolvent which is substantially unreactive with sulfuric acid. Thissolution is treated with sulfuric acid to form the monosulfo'nic acid.After the reaction a carrier oil is added to the product to facilitatehandling. The dinonylnaphthalene is initially produced by replacing someof the hydrogen atoms on the naphthalene nucleus by highly branchednonyl groups. This is brought about by alkylating the naphthalene withhighly branched nonenes, for example, tripropylene with a suitablealkylation catalyst. The King et a1. patent further discloses that thesalts are formed by neutralizing the acid with an equivalent amount ofmetal or amine. The preferred salts are those derived from the alkalineearth metals. The range of the amount of this compound in thecomposition is from 0.1 to 4 percent by weight but the preferred amountis about 1.0 percent by weight (activeingredient) basis performance.

Examples of other additives useful in this invention which are used incombination with the dinonylnaphthalene sulfonates include a metaldialkyl dithiophosphate having alkyl groups containing from 1 to 30carbon atoms which acts simultaneously as a corrosion inhibitor,antioxidant and extreme pressure agent for the base oil. Dithiophosphatemetal salts, particularly calcium and zinc salts, are produced by thereaction of metal hydroxide, oxide or metal, per se, with alkyldithiophosphates resulting from the reaction of monohydroxy aicoholswith phosphorus pentasulfide. Preferred alcohols for reaction with P 8are methyl isobutyl carbinol, isopropyl alcohol, lauryl alcohol,cyclohexanohmethyl cyclohexanol, and capryl alcohol.

Other oxidation inhibitors which are useful are the hindered phenolssuch as 2,6-di-t-butyl-4-methylphenol and alkylated diphenylamines.

Extreme pressure additives include chlorinated paraffins, sulfurizedoils, phosphorus compounds, etc.

Corrosion inhibitors include olefin-P 5 products, sulfurized wax,mercaptobenzothiazole, metal dialkyldithiocarbamates, dibasic carboxylicacids, and nonoand dialkyl phosphoric acids.

The pour depressant found to be very useful in the composition is analkylated aromatic type compound. Compounds of this type are, forexample, prepared by condensing an aliphaticcompound having a longaliphatic hydrocarbon chain such as chlorinated paraffin wax or olefinscorresponding thereto, with an aromatic compound such as naththalene,phenol, benzene, biphenyl, etc. The preferred product is obtained bycondensing about 100 parts by weight of chlorinated paratfin wax havinga chlorine content of about to percent with about 10 to parts by weightnaphthalene in the presence of aluminum chloride catalyst. Similar typepour point depressor compounds can be prepared and used in the lubricantcomposition. These are the Friedel-Crafts condensation products of lowmolecular weight alcohols (having less than 10 carbon atoms) andaromatic compounds.

Many detergent additives were bench tested to determine whether theirWater-separating properties in a lubricating oil would permit their usein a paper machine oil. The following table shows some of the results ofthe emulsion test at 180 F. (Fed. Method 791-32015). In each case thedetergent was added in the amount of about 1 percent (active ingredient)to the base oil, consisting of a mixture of about one-third parafindistillate and two-thirds parafiin residual oil having a gravity API of26.7, an SUS viscosity at 100 F. of 658, apourpoint of -10 F. and aviscosity index of 83.1,about 0.1 percent by weight of a chlorinatedparaffin wax-naphthalene condensation product and 150 ,p;p.m. (added) ofa '10 percent solution of dimethyl silicone polymer in-kerosine.

4 e TABLE I Emulsion test at F.

H O Separa- Run Detergent tion at 60 mln., cc.

None 40 (45 min.). Neutral barium dinonylnaphthalene sulionatc. 40 (5min.) Sodipm sulfonate (petroleum) 33g 28 30 0 36 Neugral calciumsulionate (petroleum) 3g 0 Neutral barium sulionate (dl-wax benzeue).---10 Basic calcium sulfonate (petroleum) 10 Basic barium sulfonate (di-waxbenzene) 30 Basic barium sulionate (petroleum). 30 Calcum phenolatesulfide g 0 The above table shows representative detergent compoundstested. None of these detergents demonstrated the excellentwater-separating properties that the salt of the dinonylnaphthalenesulfonic acid lent to the base oil. This sulfonate, surprisingly, is theonly detergent found which improved the water separating properties ofthe blends containing it, as seen in runs 1 and 2.

The process and lubricant composition of the invention were evaluated ina bench test developed to simulate the sequence of events through whichthe circulating oil is put during the paper drying operation. Thissequence can be depicted as follows:

(l) As the oil is passed through the system it is quickly contaminatedby water and is very shortly saturated therewith. The excess water isseparated out in the settling portion of an oil reconditioning apparatusincorporated in the circulating system. However, the oil remainssaturated with water.

(2) If any of the additives in the mineral oil are sensitive to water orare capable of being leached by water, this action will occur from thevery beginning and before a measurable oxidation occurs. Thissensitivity or leaching action would be greatly accelerated in machinesshowing high water contamination.

(3') Very slowly, oxidation of the oil takes place with accompanyingdegradation of the lubricant composition. Deposits and gel formationbegin to build up in the filtering portion of the oil reconditioningsystem. The filtering medium is generally a cellulose fabric, such ascotton fiber which is subject to deterioration in contact with aqueoussolutions of acidic decomposition products of the additives. Activeclay-type filters cannot be used in this service since they selectivelyadsorb the additives from the oil and lower their effectiveness.

The paper machine oil bench test to which the oil composition of theinvention was subjected consisted of thoroughly water washing the testoil with an equal volume of water. After repeating this water washingstep a second time, the water-washed oil was then subjected to oxidationat 200 F. in the presence of iron and copper, with 2 (wt.) percent wateradded daily. One liter of air per minute was bubbled through theoil-water mixture. Strips of filter bag material were added at thebeginning of the test to the test oil in order to determine the extentof deterioration caused by the test oil. The actual test conditions wereas follows: 2 liters of test oil were washed at 200 F. with 2 liters ofwater. The same wash was repeated. Then 1600 g. of test oil, 32 ml. ofwater, ASTM iron (steel) and copper strip oxidation catalyst (asdescribed in ASTM Test D943-53T) and two 2 x 6 in. cottonfiber-containing filter cloth strips were heated at m 200 F. in a flaskequipped with a condenser while .1 liter of air per minute was bubbledtherethrough. 32 ml. of water (2 percent) was added daily. Water fromthe bottom of the flask was removed weekly (except after "l68'hours).

Two. paper machine circulating'oil compositions were tested forcharacter changes while being subjected to the above procedure. Thecomposition of the invention consisted of a mineral lubricating baseoil, which was a mixture of about one-third parafiin distillate andtwo-thirds paraffin residual oil, having a gravity API of 26.5, aviscosity SUS at 100 F. of 653, a pour point of F. and a viscosity indexof 85, 2.0 (wt) percent of a 50 percent concentrate of bariumdinonylnaphthalene sulfonate in a light mineral oil, 0.75 (wt) percentof zinc dimethylisobutyl carbinyl dithiophosphate, 0.10 (wt.) percent ofa chlorinated parafiin wax-naphthalene condensation product, and 150p.p.m. (added) of a 10 percent solution of dimethyl silicone polymer inkerosene. This composition, for convenience, will hereinafter bedesignated lubricant A.

The composition used for comparison was one showing relatively goodresults in the field prior to this invention and consisted of about thesame base oil as mentioned above for lubricant A, about 2.0 (wt.)percent of a 50 percent concentrate of a neutral calcium petroleumsulfonate in a light mineral oil, about 0.5 (wt) percent of calciumalkyl phenolate, about 0.75 (Wt) percent of zinc di-methylisobutylcarbinyl dithiophosphate, about 0.05 (.Wt.) percent of a chlorinatedparaii'ln wax-naphthalene condensation product, and 150 p.p.m. (added)of a 10 percent solution of dimethyl silicone polymer in kerosene. Thiscomposition will hereinafter be referred to as lubricant B. The resultsobtained by periodic testing while the lubricants were subjected to theoxidation conditions simulating actual paper machine operation are givenin the following tables.

Table II presents data establishing superior additive retention by thelubricant of the invention.

:TABLE II Determination of additive metals in used oil samples LubricantA Lubricant B Hours Percent Percent Percent Percent Percent Percent Ba.Zn P Ca Zn P 0 after Water wash 504 TABLE III 6 following table showsthe visual observations made of the water layer which was separated fromthe oil compositions after 504 hours and after 1008 hours.

TABLE IV Visual observations of water layer The above observation ofgreen color in the water layer separated from lubricant B was indicativeof a high amount of copper which suggested an attack of some kind oncopper by lubricant B. An analysis of the water layer separated fromlubricant B showed 0.011 percent copper and 0.029 percent iron after1008 hours whereas only 0.05 p.p.m. of copper and about 0.01 p.p.m. ofiron were found in the water layer separated from lubricant A.

The antiwear characteristics of the lubricant of. the invention havebeen determined by means of the paper machine oil wear test performed onthe Shell four-ball extreme pressure lubricant tester. In this test the'SKF steel balls of 0.5 inch diameter are cleaned with Stoddard solventand MEK, dried and locked in position in the test cup. A charge of 10 to15 cc. of the test lubricant is then put into the test cup. A test runconsists of at least 2 hour runs at 600 r.p.m., 300 F. and a 15 kg. loadon the balls. The mean scar diameter on the three lower balls for eachrun is recorded. The value reported on a test consists of the average ofthe results of the two runs if they are within 0.020 mm. of each other.If they are not within this limit, a third'run is made and the valuereported is the average of these three runs. The following table givesthe results of this test on lubricant A and lubricant B, at varioustimes during their exposure to the simulated service operation.

TABLE V Paper machine oil wear test The extreme pressure and wearcharacteristics of lubricant A are definitely shown in the above tableto Visual observation: 0 copper and iron strips 504 Hours Metal 1,008Hours Lubricant A Lubricant B Lubricant A Lubricant B Black stain IronClean, except for slight stain at bottom.

Fitted, no stain-..

Black stain, trace removed at bottom.

Clean, except for 25% smooth black stain on bottom, no pitting.

Most of surface etched. Remainder black, flaking deposit. Deeply pitted,rusted. Black deposit.

Obviously, the corrosion resistance of lubricant A, is much superior tolubricant B as observed from the condition of the copper and iron(steel) strips at the termination of the test procedure. The lack ofpitting on the iron (steel) strips in lubricant A is extremelysignificant since pitting on bearing surfaces is known to be a chiefcause of bearing failures. I

In addition to the above evidence of corrosion resistbe very superior tolubricant B." This fact is further proof of the greater additiveretention of the lubricant of the invention.

The excellent properties of the oil composition of the invention,lubricant A, under extreme conditions as demonstrated in the foregoingtables prove that the addi-t-ives which lend these properties to the oilare not readily leached by high water contamination of the oil.

arm by lubricant A as compared to lubricant B, the 7 As further evidenceof this, the tensile strength at the TABLE VI Neutralization numberdetermination of oil composition Hours Lubricant Lubricant 0. 03 0. 0933 0.09 0. 08 alk 504 0. 04 0. 13 840 0. 08 0. 89 1,008 0.53 1. 07

It is quite evident from the above table that the Neut. No. rise of thelubricant of the invention is much slower that that of lubricant B whichcontains the prior art sulfonate as a detergent. This indicates muchbetter protection against oxidation.

The following table shows further evidence of the excellent oxidationresistance of lubricant A" as compared to lubricant B after 504 hours ofexposure to the condition of the paper machine oil bench test.

TABLE VII Visual observations of filtered samples 504 Hours ObservedMatter Lubricant A Lubricant B Filtered Oil Green bloom no oxi Darkbrown, oxidized dized odor. 0 or. Preclpltate TrueeofyellowbrownConsiderable dark sludge. brown sludge.

The visual observations depicted in the above tables present furtherindication of the excellent oxidation stability of the lubricant of theinvention under wet conditions. The lubricant B more readily darkenedand developed an oxidized odor. The considerable dark depositsprecipitated from the filtered lubricant B resembled the gel formationobtained from deteriorated bags in field operation. Lubricant A wassuperior in all cases in the testing for oxidation stability under.these severely wet conditions.

The advantages of the method of lubricating a machine under wetoxidizing conditions, such as are met in the dryer section of a papermaking machine, have been made obvious from the foregoing description.The use of the salt of dinonylnaphthalene sulfonic acid in place of theordinary metal sulfonates which lend equal detergency to the base oilunder dry conditions is manifest. The metal dinonylnaphthalene sulfonatedoes not promote water sensitivity nor does it act as an emulsifier.Instead, it lends water-separating properties to the base oil and givesgood detergency without becoming leached or causing other additives inthe composition to be leached. The method of lubricating a paper machinedryer section or other machinery under wet conditions utilizing acirculating oil comprising a mineral base oil with a detergent amount ofa metal dinonylnaphthalene sulfonate in accordance with this inventionis a tremendous improvement in the field of lubrication.

Obviously, many midifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof and,

therefore, only such limitations should be imposed as are indicated inthe appended claims.

We claim: t

1. A method of lubricating a machine wherein the lubricant is exposed towater contamination which comprises circulating an oil compositionthrough the bearings and gears of said machine consisting essentially ofa mineral lubricating base oil, a detergent amount of a compoundselected from the group consisting of alkaline earth metal, magnesium,zinc, and amine salts of dinonylnaphthalene sulfonic acid wherein thenonyl groups are highly branched, and an antioxidant compound in anamount suflicient to inhibit mineral oil oxidation, periodicallyremoving that portion of water which readily separates from the oilcomposition, and then recirculating said composition through thebearings and gears of said machine.

2. A method of lubricating a machine wherein the lubricant is exposed towater contamination which comprises circulating an oil compositionthrough the bearings and gears of said machine consisting essentially ofa mineral lubricating base oil, a detergent amount of an alkaline earthmetal dinonylnaphthalene sulfonate wherein the nonyl groups are highlybranched, and an oilsoluble metal dialkyl dithiophosphate wherein thealkyl groups contain from 1 to 30 carbon atoms in an amount sufiicientto inhibit oxidation of the composition, periodically removing thatportion of water which readily separates from the oil composition, andthen recirculating said composition through the bearings and gears ofsaid machine.

3. A method of lubricating a machine wherein the lubricant is exposed towater contamination comprising circulating an oil composition throughthe bearings and gears of said machine consisting essentially of amineral lubricating base oil, from 0.1 to 4 percent by weight of bariumdinonylnaphthalene sulfonate wherein the nonyl groups are highlybrowned, and from 0.1 to 2 percent by Weight of an oil-soluble Zincdialkyl dithiosphosphate wherein the alkyl groups contain from 1 to 30carbon atoms, periodically removing that portion of water which readilyseparates from the oil composition, and then recirculating saidcomposition through the bearings and gears of said machine.

4. A method of lubricating a machine wherein the lubricant is exposed towater contamination comprising circulating an oil composition throughthe bearings and gears of said machine consisting essentially of amineral lubricating base oil having an SUS viscosity at F. of from 50 to2500, about 1 percent by weight of barium dinonylnaphthalene sulfonatewherein the nonyl groups are highly branched, about 0.5 to 1 percent byweight of zinc di-methylisobutyl carbinyl dit'niophosphate, about 0.05to 1 percent by weight of a chlorinated paraflin Waxnaphthalenecondensation product, and a foam inhibiting amount of a dimethylsilicone polymer, periodically removing that portion of water whichreadily separates from the oil composition, and then recirculating saidcomposition through the bearings and gears of said machine.

5. A circulating oil composition for lubricating machinery under wetconditions which comprises a mineral base oil having an SUS viscosity at100 F. of from 50 to 2500, barium dinonylnaphthalene sulfonate whereinthe nonyl groups are highly branched, in an amount ranging from 0.1 to 4percent by weight of the composition, and an oil-soluble zinc dialkyldithiophosphate wherein the alkyl groups contain from 3 to 12 carbonatoms in an amount ranging from 0.1 to 3.0 weight percent based on thecomposition.

6. A circulating oil composition for lubricating machinery under Wetconditions which comprises a mineral base oil having an SUS viscosity at100 F. of from 50 to 2500, barium dinonylnaphthalene sulfonate whereinthe nonyl groups are highly branched, in an amount ranging fror 0.5 to 2percent by weight of the composition, zinc di-methylisobutyl carbinyldithiosphosphate in an amount ranging from 0.5 to 1 percent based on thecomposition, about 0.05-1.0 percent by weight of a chlorinated paraffinwax-naphthalene condensation product, and a foam inhibiting amount of adimethyl silicone polymer.

References Cited in the file of this patent UNITED STATES PATENTS 102,723,236 Assefi et a1 Nov. 8, 1955 2,764,548 King et al Sept. 25, 1956FOREIGN PATENTS 727,283 Great Britain Mar. 30, 1955 756,523 GreatBritain Sept. 5, 1956 OTHER REFERENCES Petroleum Refining WithChemicals, Kalichevsky- Kobe, 1956, Elsevier Publishing Company, N.Y.Pages 532 and 649-651.

Pulp and Paper Magazine of Canada, March 1950, page 94.

Lubrication, vol. 39, No. 3; March 1953, pub. by the Texas Company,pages 4244.

1. A METHOD OF LUBRICATING A MACHINE WHEREIN THE LUBRICANT IS EXPOSED TOWATER CONTAMINATION WHICH COMPRISES CIRCULATING AN OIL COMPOSITIONTHROUGH THE BEARINGS AND GEARS OF SAID MACHINE CONSISTING ESSENTIALLY OFA MINERAL LUBRICATING BASE OIL, A DETERGENT AMOUNT OF A COMPOUNDSELECTED FROM THE GROUP CONSISTING OF ALKALINE EARTH METAL, MAGNESIUM,ZINC, AND AMINE SALTS OF DINONYLNAPHTHALENE SULFONIC ACID WHEREIN THENONYL GROUPS ARE HIGHLY BRANCHED, AND AN ANTIOXIDANT COMPOUND IN ANAMOUNT SUFFICIENT TO INHIBIT MINERAL OIL OXIDATION, PERIODICALLYREMOVING THAT PORTION OF WATER WHICH READILY SEPARATES FROM THE OILCOMPOSITION, AND THEN RECIRCULATING SAID COMPOSITION THROUGH THEBEARINGS AND GEARS OF SAID MACHINE.
 5. A CIRCULATING OIL COMPOSITION FORLUBRICATING MACHINERY UNDER WET CONDITIONS WHICH COMPRISES A MINERALBASE OIL HAVING AN SUS VISCOSITY AT 100*F. OF FROM 50 TO 2500, BARIUMDINONYLNAPHTHALENE SULFONATE WHEREIN THE NONYL GROUPS ARE HIGHLYBRANCHED, IN AN AMOUNT RANGING FROM 0.1 TO 4 PERCENT BY WEIGHT OF THECOMPOSITION, AND AN OIL-SOLUBLE ZINC DIALKYL DITHIOPHOSPHATE WHEREIN THEALKYL GROUPS CONTAIN FROM 3 TO 12 CARBON ATOMS IN AN AMOUNT RANGING FROM0.1 TO 3.0 WEIGHT PERCENT BASED ON THE COMPOSITION.